North American Stratigraphic Code

Abstract

At present, there is a renewed interest in Stratigraphy due to its integrative and synthetic nature regarding very diverse information, as well as its ability to provide a rigorous terminology that serves as an effective communication vehicle, not only among Earth Science specialists but also for other fields of knowledge that utilize geological data. Satisfying this need was the central objective of the first International Geological Congresses and, in fact, it is a task that continues today, given the emergence of new discoveries that require appropriate terminology, which leads to modifying what is already available, proposing new technical terms and, of course, harmoniously and parsimoniously integrating new knowledge with the existing one.

Stratigraphic codes and guides crystallize the efforts of the geological community to provide themselves with instruments that promote the dictum "a single term for each concept," which constitutes the core of effective communication, whether scientific or of any other nature, avoiding confusion and conceptual vagueness, allowing the reproducibility of observations and the unequivocal understanding of ideas expressed by others. For a code or guide to adequately serve the community to which it is addressed, it must remain updated and faithfully reflect its work. Therefore, the North American Commission on Stratigraphic Nomenclature (NACSN) has maintained a permanent effort to update the North American Stratigraphic Code (NASC), which culminated in the 2005 publication of the revised version of the one existing since 1983, translated into Spanish and published that same year under the auspices of the Institute of Geology, UNAM, the Mexican Geological Society, and the Mexican Association of Petroleum Geologists.

The Spanish version of the 2005 NASC is presented here, hoping that, like the previous one, it will enjoy the same approval and warm reception. In this translation, the Mexican Geological Survey joins this task, which, as of 2008, has representation before the Commission. This version results from the joint work of an ad hoc committee composed of five members, all of them Stratigraphy professionals, who exchanged information electronically and, during several sessions, discussed, resolved differences, and agreed to integrate their contributions into a single document. It is worth noting that the 1983 translation, carried out by Geol. Eng. Magnolia Sánchez-López and Lic. Lía Cabib-Levi, was used as a work base, and we are pleased to recognize their effort.

In this new version, particular care was taken to preserve the spirit of the 2005 NASC; errors that had slipped into the previous one were corrected and some changes were introduced, which are detailed as follows: (1) In General Procedures, Art. 7b, it is indicated that the Institute of Geology of the UNAM, in Ciudad Universitaria, D. F., has a compendium of the formal geological units of Mexico; however, this is not the case; in reality, it is the Mexican Geological Survey that, through its Stratigraphic Lexicon of Mexico (LEM) project, is compiling and systematizing the relevant information, which can be consulted on the Mexican Geological Survey portal http://www.sgm.gob.mx/. (2) Regarding the nomenclature of lithostratigraphic units, Art. 25c and 26, the terms lengüeta and capa are replaced respectively by lengua (tongue) and estrato (bed or strata as appropriate), both in common use. (3) Regarding biostratigraphic units, Art. 50, the term hemerozona (hemerozone), recommended by the International Stratigraphic Guide, is used here to identify in a separate class of biostratigraphic unit the types of interval zones, originally defined as “taxon-range biozone” and “concurrent-range biozone”; furthermore, the term biozone is used uniformly instead of zone. (4) With reference to the so-called edafostratigraphic units, Arts. 55 and 56, after consultation with national and Latin American soil scientists, it was decided to redesignate them as Pedostratigraphic Units, as this is more appropriate; also, current soils are distinguished and contrasted from paleosols or “geosols”. (5) In the case of diachronic units, Art. 93, the terms intervalo (interval) and digitación (fingering) were replaced respectively by lapso (span) and clino (clino), which better reflect the meaning of the corresponding English terms.

On the other hand, this ad hoc committee thanks Dr. Randall Orndorff, of the United States Geological Survey and the NACSN, for sending the original electronic files of the figures; Lic. Angélica Montiel Beltrán, of the Mexican Geological Survey, skillfully prepared the figures for this version. Finally, our gratitude to Dr. Carlos Manuel González León for the critical review he performed on the manuscript of this translation, thus helping to improve its quality.